Hello, I want to supply an ATMEGA16 and sim800 module with a 3.7 Li-ion battery, so i used XL6009 module (not IC, figure below) to convert 3.7 to 5V. When just uC is connected to the output of XL6009 everything is ok and output is 5V, but when I connect sim800 module, XL6009's output rises to about 10 Volt!! I even connect the converter module to sim800 module out of PCB and the same problem happened. What can be the problem?!

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